Prosthetic cardiac valves have been used for many years to treat cardiac valvular disorders. The native heart valves (such as the aortic, pulmonary and mitral valves) serve critical functions in assuring the forward flow of an adequate supply of blood through the cardiovascular system. These heart valves can be rendered less effective by congenital, inflammatory or infectious conditions. Such damage to the valves can result in serious cardiovascular compromise or death. For many years the definitive treatment for such disorders was the surgical repair or replacement of the valve during open heart surgery, but such surgeries are prone to many complications. More recently a transvascular technique has been developed for introducing and implanting a prosthetic heart valve using a flexible catheter in a manner that is less invasive than open heart surgery.
In this technique, a prosthetic valve is mounted in a crimped state on the end portion of a flexible catheter and advanced through a blood vessel of the patient until the prosthetic valve reaches the implantation site. The prosthetic valve at the catheter tip is then expanded to its functional size at the site of the defective native valve such as by inflating a balloon on which the prosthetic valve is mounted. Alternatively, the prosthetic valve can have a resilient, self-expanding stent or frame that expands the prosthetic valve to its functional size when it is advanced from a delivery sheath at the distal end of the catheter.
The native valve annulus in which an expandable prosthetic valve is deployed typically has an irregular shape mainly due to calcification. As a result, small gaps may exist between the expanded frame of the prosthetic valve and the surrounding tissue. The gaps can allow for regurgitation (leaking) of blood flowing in a direction opposite the normal flow of blood through the valve. To minimize regurgitation, various sealing devices have been developed to seal the interface between the prosthetic valve and the surrounding tissue.
A disadvantage of many sealing devices is that they tend to increase the overall profile of the prosthetic valve in the compressed state. A prosthetic valve that has a relatively large profile or diameter in the compressed state can inhibit the physician's ability to advance the prosthetic valve through the femoral artery or vein. More particularly, a smaller profile allows for treatment of a wider population of patients, with enhanced safety. Thus, a need exists for sealing devices that do not contribute significantly to the overall crimp profile of the prosthetic valve.